Process of cementing iron or steel.



No- 799,542. PATENTED SEPT. 12, 1905.

G. G. DAVIS.

PROCESS OF CEMENTING IRON 0R STEEL.

APPLICATION FILED NOV.15, 1904.

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CHARLES C. DAVIS, OF GERMANTOIVN, PENNSYLVANIA.

PROCESS OF CEIVIENTING IRON OR STEEL.

Specification of Letters Patent.

Patented Sept. 12, 1905.

I Application filed November 15, 1904. Serial No. 232,787-

To all whom it may concern.-

Be it known that I, CHARLES C. DAvIs, a citizen of the United States,residing at Germantown, in the county of Philadelphia and State ofPennsylvania, have invented certain new and useful Improvements inProcesses of Cementing Iron or Steel, of which the following .is aspecification.

My invention relates to an improved method .of cementing orsupercarburizing steel or iron articles, especially adapted forproducing a decrementally-hardened surface, such as re.

veniently obtained by establishing an electric arc between a carbonelectrode and the surface under treatment or by passing a sufiicientlyheavy electric current through a layer of granular carbonaceous materialin contact with the article under treatment to generate an intense heatby the resistance of such carbonaceous layer. This proposed use of anelectric current for the purpose of producing intense local heating ofthe surface during the cementation process causes burning anddeterioration of portions of the surface under treatment and has provenimpracticable.

In the operation of my invention the article under treatment ispreferably maintained at a nascent cherry heat in contact with suitablecarbonaceous material, and a direct electric current is passed throughthe carbonaceous material and article to cause rapid absorption of thecarbon by the latter without raising the temperature in such circuit.The advantageous action of the electric current in the practice of myinvention seems to reside primarily in producing a beneficialrearrangement of the atoms of the iron or steel article under treatmentand also in producing a more uniformly graduated penetration of thecarbon in the said articles, thereby expediting the absorption of carbonand producing a uniform decremental hardening of the entire surfaceunder treatment.

In the accompanying drawings, forming a part of this application, and inwhich similar reference-numerals indicate corresponding parts in bothviews, Figure 1 is a vertical sectional view taken on theline 1 1 ofFig. 2,'illustrating more or less diagrammatically one arrangementforcarrying outmy invention; and Fig. 2 is a plan View of the parts shownin Fig. 1.

Referring to the drawings, 1 indicates a steel truck or other suitablecarrier supporting two armor-plates 2 and 3, together with an interposedelectrode, such as an iron plate 4:. A layer of suitable carbonaceousmaterial 5 is packed between the plate 4: and the adjacent faces of thearmor-plates 2 and 3. Such carbonaceous material may consist ofgraphite, coal, or coke, which may be mixed with sand, silica, bariumcarbonate, or other suitable material for adjusting the electricalresistance of the layer. A wall 6 of fire-brick or otherheat-non-conducting material is shown surrounding the several elementsfor effectively preventing entrance of air to the faces of the platesunder treatment. The plate 4 is provided with suitable means, such as alug 7, for connecting it to the positive pole of a source of electricalenergy, and the armorplates 2 and 3 are provided with similar means 8and 9 for convenient connection to the negative pole of said electricalsupply.

The operation of my invention is as follows: The armor-plates 2 and 3are placed in a furnace with suitable carbonaceous material 5 packedbetween them and a common interposed positive electrode l, means, suchas-a fire-brick wall 6, being employed to prevent access of air to thecarbonaceous material. The parts thus assembled are raised to andmaintained at a temperature of approximately 800 centigrade to 850centigrade. A direct electric current of suitable strength and characteris then passed from the common positive electrode ithrough thecarbonaceous material and armor-plates to cause a rearrangementof theatoms of said plates and expedite the absorption of carbon therebywithout pro- 1 ducing an appreciable increase of temperature by theresistance of said circuit. This operation is continued until thedesired degree of cementation is produced, after which the plates areslowly cooled in the usual manner to prevent strains and distortion.

I have illustrated and described a single means for carrying out myinvention; but obviously it is applicable in other manners.

ITO

Having thus described my invention, what I claim, and desire to secureby Letters Patcm, is-

- 1. The herein-described process of cementing or carburizing steel oriron, which consists in maintaining the article at a nascentcherry heatin contact with carbonaceous ma terial, and simultaneously passing adirect electric current of suitable strength and character through saidcarbonaceous material and article to cause a rearrangement of the atomsof said article, substantially as described.

2. The herein-described process of cementing or carburizing steel oriron, which consists in maintaining the article at a temperature ofapproximately 800 centigrade to 850 centigrade in contact withcarbonaceous material, and simultaneously passing a direct electriccurrent of suitable strength and character through said carbonaceousmaterial and article to expedite the absorption of carbon by the latter,substantially as described.

3. The herein-described process of cementing or carburizing steel oriron, which consists in maintaining the article at a temperature ofapproximately 800 centigrade to 850 centigrade in contact withcarbonaceous material, simultaneously passing a direct electric currentof suitable strength and character through said carbonaceous materialand article to expedite the absorption of carbon by the latter, andexcluding the parts under treatment from access of the atmosphere,substantially as described.

4. The herein-described process of cementing or carburizingarmor-plates, which consists in packing carbonaceous material betweentwo armor-plates and a common positive electrode interposedtherebetween, maintaining the parts so arranged at a temperatureapproximately 800 centigrade to 850 centitive electrode interposedtherebetween, main-v taining the parts so arranged at a temperatureapproximately 800 centigrade to 850 centigrade, simultaneously passingfrom such com- -mon electrode through the carbonaceous material andplates a direct electric current of suitable strength and character toexpedite the absorption of carbon by the latter, and excluding theopposing faces of said plates from access of the atmosphere,-substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

CHARLES C. DAVIS. Witnesses:

E. B. PEAoo'oK, H. BERENS.

